**5. Discussion**

Annually, the investigated regional power supply company "Oreolenergo", a branch of IDGC of Center, has an average of 344 power supply outages with a total of 98,495.835 kWh of unsupplied electric power [17]. The total number of power outages includes consumer outages, outages due to damage of overhead lines, cable lines, transformers, equipment of transformer substations, and distribution points. The average power supply restoration time is 5.86 h, which is close to the time obtained based on the performed studies (5.28 h). The deviation is 9.9%. It should be noted that these data on the power supply restoration time are related to failures in power transmission lines, which are the most unreliable element of the power supply systems.

A power supply restoration time of more than 5 h causes significant damage both to consumers and to power supply companies. Opportunities should be sought to shorten this time as much as possible. In most cases, it is difficult, since a noticeable number of power lines especially in rural areas have surpassed their resources and require replacement [39,40]. According to the statistical data of "Oreolenergo" [17], the causes of damage to power lines are shortcomings in maintenance (45%), the influence of natural and weather conditions (33%), the influence of unauthorized persons (15%), other reasons (e.g., birds, animals, etc.) (7%). At the same time, it is indicated that shortcomings in maintenance includes fallen trees and short circuits because of trees touching power line wires caused by untimely cleaning of power line routes, breaks of wires, fallen utility poles, and other causes associated with power line aging and late monitoring of their condition.

The PS restoration time may be reduced by different methods, especially the electrical network automation means. Almost all automation means can reduce the time to perform a particular operation and increase the accuracy of its execution. For example, the time to obtain information and recognize it can be significantly reduced by using a power supply reliability monitoring system or by using means for monitoring the technical condition of an electric network equipment, such as using unmanned aerial vehicles (UAVs) as in the articles [41–44] or the thesis [45]. Calculations realized in [45] indicated the implementation of the developed power supply reliability monitoring system in the Mtsensky electric grid of the Orel Region, Russian Federation. They showed that the time to obtain information

was reduced from 1.01 h to 0.09 h, and the time to recognize information was reduced from 2.30 h to 0.25 h. In [46], UAV tests were described based on the Orelenergo branch of the IDGC of Center, PJSC. They showed that it was possible to achieve a reduction in the time of a PTL round check (the time for recognizing information) from 3.5 h/km to 5 ... 15 min/km, that is, more than 30-fold.

It should be noted that if there are means of sectionalizing and redundancy of power lines such as automatic circuit reclosers (ACR), the time of power supply outages can also be significantly reduced [47,48]. However, in this case, the power supply restoration will be carried out by redundancy means, and the time for this restoration *t*restor.redund. is determined by the equation

$$t\_{\text{restor.reduced}} = t\_{\text{damaged}\,\,\text{section isol.}} + t\_{\text{backup power act.}} \tag{21}$$

where *t*damaged sec tion isol. is the time spent on the isolation of the damaged section from intact ones, h; *t*backup power act. is the time spent on backup power actuation, h.

All means of electrical network automation can be classified according to the time intervals that they shorten. This classification is shown in Table 5. Thus, the existing and promising methods and technical means of electrical network automation aim at reducing the specific constituents of the power supply restoration time.


**Table 5.** Methods and technical means of electrical network automation for reducing the power supply (PS) restoration time.
